YLS-3000 Fiber Laser Melting and Quenching of 42CrMo Steel

Laser quenching is one of the important methods for strengthening the surface of materials. When laser quenching is performed on metal materials, due to the rapid heating and cooling effect of the laser on the surface of the material, high-carbon twin martensite and high dislocations can be obtained on the surface. Density of austenite, sorbite and hard carbides have good wear resistance and corrosion resistance, which greatly improves the surface properties of the material. Some existing research results have revealed the influence of power and scanning speed on the depth and hardness of the hardened layer during laser phase transformation quenching, but there are few studies on the factors affecting the fusion quenching process. There will be some deformation on the surface after fusion and quenching, but because it can obtain a deeper hardened layer, its application prospects are also relatively large. The 42CrMo steel was used for laser melting and quenching test, and the influencing factors of the structure and performance after quenching were analyzed from the laser power and scanning speed. The technicians of the Chinese Academy of Ordnance Science used YLS-3000 fiber laser to perform surface fusion quenching treatment on 42CrMo steel; after quenching, the sample was cut in the middle of the sample with a laser cutting machine along the direction perpendicular to the scanning direction for inspection; the hardened layer was displayed. The microstructure was observed on the ZEISSImager.A2m metallurgical microscope and Hitachi S-3400 scanning electron microscope; the hardness was measured on a domestic small-load Vickers hardness tester, and the depth of the hardened layer was determined by the Vickers hardness method with metallographic pictures. The test steel is 42CrMo structural steel, which is processed into a 20mm×20mm×10mm sample; the hardness of the sample matrix is u200bu200b310HV, and the surface roughness of the material is 3.0. The sample is cleaned with acetone before quenching. The mass fraction of the alloy composition of the sample is ：0.54C, 1.32Cr, 0.39Mo, 0.45Si, 0.78Mn, Fe balance. The test results show that: 　　 laser melting quenching hardened layer depth increases with the increase of laser power and scanning speed decreases, and decreases with the decrease of laser power and scanning speed, where the laser power has an effect on the depth of the hardened layer Greater impact. The laser power is 1500W and the scanning speed is 200mm/min for laser melting and quenching. The surface appearance quality is good. The surface melting zone is about 0.3mm deep, and its hardness is slightly lower than that of the inner side. The average hardness of the hardened layer is about 660HV and the average depth is about 2mm. . It can be seen that the hardness of laser melting quenching is about 10% higher than that of conventional quenching. By comparison, it is found that the maximum hardness value is near 0.3mm from the surface, and with the increase of scanning speed, the hardness increases, and the increase range is about 6%.　　The center of the melting area of u200bu200bfusion quenching will have an expansion deformation of 0.1～0.2mm, and the edge will show a shrinkage deformation of about 0.1mm. When performing fusion quenching, a machining allowance of 0.2mm is required.